added word break solution

LeetCode/word_break.cpp

@@ -0,0 +1,28 @@
+// Word break memoization solution
+
+class Solution {
+public:
+    unordered_map<string,int> mpp;
+    int dp[501];
+
+    bool get(string s,int index){
+        if(index==s.size())return true;
+        if(dp[index]!=-1)return dp[index];
+        string tmp="";
+        bool ok=false;
+        for(int i=index;i<s.size();i++){
+            tmp+=s[i];
+            if(mpp[tmp]>0){
+                ok=(ok|get(s,i+1));
+            }
+        }
+        return dp[index]=ok;
+    }
+
+    bool wordBreak(string s, vector<string>& wordDict) {
+        for(auto el:wordDict)mpp[el]++;
+        for(int i=0;i<501;i++)dp[i]=-1;
+        bool ans=get(s,0);
+        return ans;
+    }
+};